The breakdown voltage and on-resistance of a multi-RESURF LDMOS are studied numerically and analytically. The results are compared with those from the conventional LDMOS. Reduction of on-resistance by 23% is obtained for the multi-layer structure without degradation in the breakdown voltage. An analytical expression for the surface potential distribution of the multi-layer structure is derived which provides a useful mean to determine the breakdown voltage analytically in terms of the device parameters.